My client will be migrating from POP email servers to Hosted Exchange later in the year.
In the time being, there are several email address(es) that are not getting to the POP email users.
I have cpanel access to the POP email server.
I have ensured that the client's domain is whitelisted and not being blocked by any of the MX providers.
Is there anyway, other than speaking to the owners of the email address(es)/domains to verify why my client's users are not getting emails?